Hello TechNet.

        I am looking for information regarding two unsolved mysteries I
have encountered:

1)  I am able to remove a PBGA388 from a 17 layer (0.125" thick) PWB,
but cannot place a new device.  The BGA substrate seems to be warping
and I am getting non-soldered (open) interconnects at the corners of the
BGA.  The rework equipment used is an Air Vac DRS26 (hot gas -
nitrogen).  If I reduce the temperature or time on the rework profile,
to try and reduce BGA warpage, reflow is not achieved at all
interconnects.  Has anyone come across a similar problem and found a
solution?


2)  After assembly reflow (forced convection system), one to three balls
of a particular BGA, in the same location(s) disappear!  The X-ray shows
no trace of solder on the BGA land pattern of the PWB or BGA substrate.
The surrounding balls are all present and not visibly oversized.  All
PWB BGA land patterns are NSMD, with dog-bone configuration for vias,
with soldermask between the land and the via.  The vias are also tented.
Has anyone come across this problem?



Thanks,

Ernst Wallisch
Manufacturing Engineering
Computing Devices Canada
(613) 596-7536
[log in to unmask]

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